Power module with a circuit arrangement comprising active semiconductor components and passive components, and method for producing same

ABSTRACT

The invention relates to a power module with a circuit arrangement provided with active semiconductor components and passive components and with a circuit substrate, whereby at least a portion of the active semiconductor components are soldered onto a DCB substrate and at least a portion of the passive components are printed in thick film technology on at least one ceramic substrate. The upper side of the DCB substrate is structured to form track conductors and connecting surfaces for receiving the active semiconductor components and passive components of the circuit arrangement. On the ceramic substrate, for each passive component, a first print layer is printed in thick film technology and at least one contact surface as additional print layer laterally adjoining the first print layer. The ceramic substrates for the passive components in thick film technology are connected via the at least one contact surface with the corresponding connecting surface(s) of the DCB substrate by means of a soldered connection.

[0001] Power modules are used in many application fields for varioustasks, for example, to control the speed and power of electric motors. Acircuit arrangement acting as power unit forms part of such powermodules and typically has both active semiconductor components, such aspower semiconductor components, and passive components, such asresistors (e.g., shunts for current measurement) and possiblycapacitors. The power semiconductor components work in switched mode,which causes high rates of current change. These high rates of currentchange necessitate a low-inductance structure of the circuit arrangementto prevent overvoltages.

[0002] Consequently, and for reasons of adequate heat removal of theirpower dissipation, the carrier element used for the circuitarrangement's active semiconductor components (particularly the powersemiconductor components) is typically a so-called DCB (direct copperbonding) substrate, which is made of a ceramic layer enclosed by twocopper layers (e.g., made of aluminum oxide Al₂O₃). The activesemiconductor components (power semiconductor components) are solderedto the upper copper layer of the DCB substrate and contacted by means ofbond wires. The upper copper layer of the DCB substrate is structured(interrupted) to form track conductors for connecting the powersemiconductor components.

[0003] For mechanical stabilization and heat removal, the DCB substrateis mounted on a metal plate serving as circuit substrate, typicallysoldered. This metal plate transfers the heat loss to a cooling system.

[0004] The circuit arrangement's passive components (particularly theresistors) are advantageously realized in thick film technology (i.e.,printed on a ceramic substrate). This ceramic substrate, in a separatemanufacturing step, is bonded to the circuit substrate adjacent to theDCB substrate (e.g., by means of heat conductive bonding).

[0005] The inherent disadvantage is that

[0006] separate process steps and technologies are required forsoldering the DCB substrate and bonding the ceramic substrate to thecircuit substrate, which is time-consuming and costly;

[0007] Connection (contacting) between the circuit arrangement's passivecomponents mounted on the ceramic substrates and the activesemiconductor components mounted on the DCB substrates is problematicdue to the spatial separation. This requires long connecting leads andconnecting lugs, which as parasitic inductances have a negative effecton the properties of the circuit arrangement or power module (generationof overvoltages, EMV problems).

[0008] DE 35 38 933 A1 furthermore shows a power module in which theceramic substrate carrying the passive components is soldered directlyto the DCB substrate carrying the active semiconductor components. Here,the solder connection performs a pure fixation and heat conductingfunction. Although this eliminates the additional process step ofbonding, a large number of bond wires continue to be required forelectric contacting of the passive components with the track conductorstructure arranged on the DCB substrate. Bond wires, however are costlyand susceptible to mechanical stresses.

[0009] The object of the invention is to define a power module inaccordance with the preamble of claim 1 with a simple structure andmanufacturing process, in which these disadvantages are obviated.

[0010] According to the invention, this object is attained by thefeatures of claim 1.

[0011] Advantageous further developments of the power module and aprocess for its manufacture are the subject of the additional claims.

[0012] In the inventive power module, at least a portion of the passivecomponents is realized by means of thick film technology (e.g., bydepositing on a ceramic substrate a first print layer as the actualcomponent and at least one additional print layer laterally adjacent tothe first print layer acting as contact surface). The ceramic substratethus printed (the thick film circuit) is placed on the upper side of theDCB substrate (the upper copper layer) suitably structured to form trackconductors and connecting surfaces and is connected with the DCBsubstrate by soldering the contact surface(s) to the correspondingconnecting surfaces of the DCB substrate. Connection (contacting) withthe other semiconductor components arranged on the DCB substrate can besuitably effected either directly via track conductors or via bondwires. The DCB substrate is suitably connected with the circuitsubstrate of the circuit arrangement, e.g., soldered to this circuitsubstrate (e.g., a metal plate). Power dissipation of the passivecomponents (particularly resistors) arranged on the ceramic substrate isremoved via the ceramic substrate and the DCB substrate to the circuitsubstrate. During production, the ceramic substrates with the passivecomponents (the resistors) can be soldered to the circuit substratesimultaneously to soldering the active semiconductor components and/orsimultaneously to soldering the DCB substrate to the circuit substrateso that no separate process step is required. In other words, solderingthe thick film circuit (passive components on ceramic substrate) can beexecuted simultaneously with soldering the active semiconductorcomponents to the DCB substrate or simultaneously with soldering theactive semiconductor components to the DCB substrate and the DCBsubstrate to the circuit substrate.

[0013] In addition to the components realized in thick film technology,other components (e.g., SMD components) can be mounted on the ceramicsubstrate and connected with the rest of the circuit arrangement bymeans of contact surfaces.

[0014] The advantages of said for manufacturing a power module are that

[0015] production complexity and thus cost of the power module arereduced by the simultaneously performed soldering process required forthe passive components (the resistors) onto the active semiconductorcomponents;

[0016] a simpler and more compact structure results due to the lownumber of connecting leads of the circuit arrangement and the reducedlead length of the possibly still present connecting leads;

[0017] overvoltages, and thus impairment of the functioning of the powermodule, are prevented due to the shorter lengths of the connecting leadsand the reduced parasitic inductances.

[0018] Below, the inventive power module is described by means of anexemplary embodiment in conjunction with the drawing. The FIGURE shows aschematic view of the structure of the power module in a sectionaldrawing.

[0019] The power module's circuit arrangement 1 disposed, for example,on a circuit substrate 2 with the dimensions 99 mm×57 mm×3 mm comprises,for example, a plurality of power semiconductor components 11 (powertransistors and power diodes) and a plurality of resistors 10 as shuntsfor measuring the transistor currents.

[0020] The carrier element provided for the power semiconductorcomponents 11, which are implemented as semiconductor devices, and theresistors 10, which are realized in thick film technology, is a DCBsubstrate 3, which is composed of a first copper layer 32 (structured toform track conductors and connecting surfaces), a ceramic layer 31formed as an oxide layer, and a second (unstructured) copper layer 33.The power semiconductor components 11, e.g., the power transistors andpower diodes formed as semiconductor devices (semiconductor chips), aresoldered to the connecting surfaces of the first copper layer 32 (i.e.,to the upper side of the DCB substrate 3) by means of solder 15 and aremechanically connected by this soldering process with the DCB substrate3 (of the first copper layer 32) (particularly for removal of theirpower dissipation) and are electrically conducted via bond wires 12. Theresistors 10 from the resistor track 13, the two contact surfaces 14laterally adjoining the resistor track 13 (metallizations), and aprotective layer (passivation) (not depicted) are printed on a ceramicsubstrate 21. This ceramic substrate 21, using contact surfaces 14, issoldered to the connecting surfaces provided for this purpose on theupper side of DCB substrate 3 (first copper layer 32) (by means ofsolder 15). In production, this soldering process is preferably carriedout simultaneously to soldering the power semiconductor components 11onto DCB substrate 3 and DCB substrate 3 with the mounted activesemiconductor components 11 and passive components 10 is subsequentlysoldered to circuit substrate 2, which is formed, for example, by ametallic copper plate.

1. Power module with a circuit arrangement (1) provided with activesemiconductor components (11) and passive components (10) and with acircuit substrate (2), whereby at least a portion of the activesemiconductor components (11) are soldered to a DCB substrate (3) and atleast a portion of the passive components (10) are printed in thick filmtechnology on at least one ceramic substrate (21), and whereby the upperside (32) of the DCB substrate (3) is structured to form trackconductors and connective surfaces for receiving the activesemiconductor components (11) and the passive components (10) of thecircuit arrangement (1), characterized in that, for each passivecomponent (10) provided, on a print side of the at least one ceramicsubstrate (21), a first print layer (13) determining the properties ofthe passive component (10) is printed in thick film technology and atleast one contact surface (14) as an additional print layer laterallyadjoining the first print layer (13); and that the at least one ceramicsubstrate (21) is electrically connected via the at least one contactsurface (14) with the corresponding contact surface(s) of the DCBsubstrate (3) by a soldered connection.
 2. Power module according toclaim 1 characterized in that additional components are mounted on theceramic substrate (21).
 3. Process for manufacturing a power module witha circuit arrangement (1) provided with active semiconductor components(11) and passive components (10) and with a circuit substrate (2),whereby at least a portion of the active semiconductor components (11)are soldered to a DCB substrate (3) and at least a portion of thepassive components (10) are printed in thick film technology on at leastone ceramic substrate (21) and whereby the upper side (32) of the DCBsubstrate (3) is structured to form track conductors and connectingsurfaces for receiving the active semiconductor components (11) and thepassive components (10) of the circuit arrangement (1), characterized inthat, for each passive component (10) provided, on a print side of theat least one ceramic substrate (21), a first print layer (13)determining the properties of the passive component (10) is printed inthick film technology and at least one contact surface (14) asadditional print layer laterally adjoining the first print layer (13);and that the at least one ceramic substrate (21) is electricallyconnected via the at least one contact surface (14) with thecorresponding contact surface(s) of the DCB substrate (3) by soldering.4. Process according to claim 1 characterized in that soldering of theceramic substrate (21) is carried out simultaneously to soldering theactive semiconductor components (11) to the DCB substrate (3) and/orsimultaneously to soldering the DCB substrate (3) onto the circuitsubstrate (2).
 5. Process according to claim 1 or 2 characterized inthat additional components are mounted on the ceramic substrate (21).